This invention relates to apparatus for generating ramp voltages. More particularly, it is concerned with apparatus for repeatedly providing an ascending and descending staircase ramp voltage to a capacitive load.
Capacitive type displays, such as thin film electroluminescent displays, waste a large portion of the total addressing power simply in the charging and subsequent discharging of elements which are not addressed. Typically in order to minimize charging currents a ramp voltage is applied to row and/or column address buses to charge the buses and their associated capacitive load to the appropriate voltage. The ramp voltage may be produced by selectively connecting an array of voltage sources in sequence to a bus in order to produce a staircase ramp voltage. After the appropriate time interval following the end of the ramp voltage buildup the bus is returned to ground potential. Discharging the charge stored in the capacitive load to ground is a primary cause of power loss in the operation of conventional addressing arrangements.